The vote was cast by veteran actor Simon Yam Tat-wah, who played a skilled neon sign craftsman in the film. He apologised for his mistake on Tuesday.

“To all the crew and colleagues who contributed to the film A Light Never Goes Out, I am sorry. Voting for the film was my mistake. I am very, very sorry,” Yam said.

“I’d also like to apologise to the Federation of Motion Film Producers of Hong Kong and to all who love films,” he added.

The film’s producer Saville Chan expressed regret over the incident but said learning from the experience was important.

“For a Hong Kong film representing the city to be a contender in the high-profile Academy Awards is a very important matter,” Chan said. “I hope that the rules can be clarified from now on and the misunderstanding is not repeated.”

In late September, A Light Never Goes Out was announced as Hong Kong’s entry for the best international feature film category, previously labelled as best foreign-language film.

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The film centres on Hong Kong’s once ubiquitous neon signs and follows the journey of a widow, portrayed by Sylvia Chang Ai-chia, as she carries on the legacy of her late husband, who was a master in crafting the lights. Chang’s performance won her the Golden Horse Award for best leading actress last year. The film also stars Simon Yam Tat-wah, Choi Sze-wan and Ben Yuen Fu Wah.

Federation chairman Crucindo Hung Cho-sing said the disqualification was the result of a conflict of interest in the voting process, following two changes to the selection mechanism requested by the academy in August.

The first change disqualified anyone who had taken part in the selection process for more than six years from voting again, effective immediately, he said.

The second change barred any committee member who had a conflict of interest with a film being considered from voting for it, a rule that had not been specified in the past two decades or so, he added.

In August, the academy endorsed the appointment of a new 13-person selection committee in Hong Kong, replacing the previous 19 members.

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But one actor from A Light Never Goes Out was a member of the new committee and voted for the film, which nullified the submission, Hung said.

“In the email about the change of rules, it only stated: if you’re involved in the film, there will be a conflict of interest,” he said. “But it did not spell out explicitly that they are not allowed to vote. So we misunderstood, as per the established mechanism.”

The federation chairman said the film won the nomination by far more than one vote, but the academy would not accept the result or another poll that included the feature.

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Nominating the first runner-up, A Guilty Conscience, would not be fair to the original winner given the large difference in votes, so the federation decided about a month ago to not put forward any film for the Oscars, he said.

“It is a shame that [the film] could not participate in the awards,” the federation said, adding the selection process was fair. “This is a very rare and regrettable incident.”

In a reply to a local media outlet, the academy said the submission of A Light Never Goes Out had violated submission guidelines, which stated “selection committee members cannot have a professional relationship with a film that is considered for official selection”.

Producer Chan said: “What’s more important is that in the future, we’d be able to successfully send a film to compete for Hong Kong at the Oscars every year.”

The academy earlier announced 92 submissions were made for the best international film category, but only 88 qualified.

Kenny Ng Kwok-kwan, associate professor at Baptist University’s film academy, said the misunderstanding appeared to be a schoolboy error, stressing that it might reflect a bigger issue.

“This is not a one-off incident. The Hong Kong film industry has had a long history, but what this incident shows is that the practical operations and mechanisms can be improved,” he said.

“It also raises questions on whether some organisations [in the industry] are dated and are getting out of touch with practices beyond Hong Kong.”

He also said he believed that conflict of interest had always existed, arguing that perhaps there was not an occasion that prompted the discussion of the rule in the past.

Ng highlighted that in the highly competitive industry of film, nominations and awards were very important, but they could be very dependent on cliquey relationships within the industry.

He said that the industry could work on making their nominations more representative, especially on an international stage.